This is a proposal to study the free radical chemistry of cigarette smoke, woodsmoke, smoke from plastics and elastomers, and automobile exhaust. We will elucidate the mechanisms for production of radicals in these smokes and determine the structures and reactivities of the radicals. There is considerable inferential evidence that radicals often mediate the reactions of components of these smoke streams with pulmonary target molecules. Our long-term aim is to develop insight into the chemistry of the radicals in these smoke streams so the biological reactions they initiate can be predicted and understood. Cigarette smoke places an oxidative burden on the lungs of the smoker, and the very high concentration of carbon - and oxy- radicals in smoke suggests they may be implicated in this effect. Recent evidence also demonstrates loss of pulmonary function for persons exposed to woodsmoke, which our preliminary evidence show contains even more radicals than does tobacco smoke. Our specific aims are: (1) Use FTIR and other methods to study the oxidation of N0 to N02 in tobacco smoke and in the model systems we have developed. This is a critical test of our hypothesis that the radicals in cigarette smoke are being continuously produced by NOx-olefin reactions. (2) Utilize electron-spin resonance spin- trap methods to probe which materials (wood, plastics, elastomers) burn to produce radicals and determine their yields and structures. (3) Use spin traps methods to determine the yields and structure of the radicals in both spark ignition and diesel exhaust and the effects of engine operating variables on radical yields.